ios 音量调整

  //系统的音量
    MPVolumeView *volumeView = [[MPVolumeView alloc]init];
    [self addSubview:volumeView];
    //转移到屏幕视线外的地方显示
    volumeView.frame = CGRectMake(-1000, -100, 100, 100);
    [volumeView sizeToFit];
    
    // 获取系统的音量滑块
    for (UIControl *view in volumeView.subviews) {
        if ([view.class.description isEqualToString:@"MPVolumeSlider"]) {
            systemSlider = (UISlider *)view;
            NSLog(@"%f",systemSlider.value);
            systemSlider.value = 1;// 音量为0-1
            break;
        }
    }